Nearly 700,000 open heart surgeries are performed annually in North America. During the surgery, the sternum is bisected to access the thoracic cavity, a procedure known as sternotomy. Following the primary operation, the sternum is closed, typically with wire sutures.
The sternal reapproximation procedure is generally successful. However, post operative complications occur in approximately 2% of procedures, generally in patients over the age of 65. High instances of osteoporosis that are common in this age group causes the sternum to wear away at fixation points, causing loosening within the system. When loosening occurs, other complications can arise, such as medianstinitis, or infection of the sternum, which has been shown to have a mortality rate as great as 15%.
Low cyclic forces generated by repetitive motion, such as breathing motion in the case of the sternum, can lead to unwanted loosening and even failure of the fixation system. This problem becomes even more acute in the case of osteoporotic or lower-density bones. Currently the most common practice of sternal fixation utilizes stainless steel surgical wires. However, for some patients, the low cyclic forces generated by breathing can cause the wires to cut into the patient resulting in losses of fixation and normal bone alignment. Rigid fixation techniques, such as with a plate and screw assembly, are known, but are not commonly used for sternum fixation. This is due to a variety of factors, including the length of time for the procedure and increased level of skill required by the surgeon, as well as the cost. In addition, existing plate and screw assemblies are not optimized for fixation of the sternum.